A new study finds that pollution of waterways with the antidepressant Prozac could have adverse effects on fish's physical and behavior, threatening their long-term survival.
As global consumption of pharmaceuticals increases, residues are finding their way into rivers and streams through wastewater, raising concerns about the impact on ecosystems and wildlife.
A study published in the journal Animal Ecology found that low concentrations of the antidepressant fluoxetine, commonly known as Prozac, reduced the body condition and sperm vitality of male guppies across multiple generations.
Dr Upama Aich from Monash University, co-lead author of the study, said thousands of chemicals are “dumped into our waterways every day.” The researchers chose to study fluoxetine because it's “so ubiquitous.”
Aich said the changes observed in the guppies given low concentrations of the drug should be taken as a warning about the fish's ability to survive and thrive in polluted environments.
The researchers captured 3,600 wild guppies, an invasive species from Australia, and randomly assigned them to tanks filled with gravel and aquatic plants.
Over a five-year period, the researchers administered different concentrations of fluoxetine to the tanks – zero, a low (31.5 nanograms per liter), and a high (316 nanograms per liter) concentration that match those found in the natural environment. They then studied the effects on the behavioral, physical, and reproductive characteristics of male fish across multiple generations.
Aich said low-dose radiation caused males across the population to become less physically fit, “which is very important not only for mating but also for fighting other males and for overall survival.” Low-dose radiation also reduced sperm velocity, but increased the length of the gonopodium, a fin-like organ used to fertilize females, she said.
She said exposure to the drug also reduced activity changes and risk-taking behaviour, which could affect the guppies' ability to cope with changes in the wild.
Dr Minna Saarist, chief scientist for ecological risks and emerging contaminants at Victoria's Environment Protection Agency, said medicines are designed to be effective at low doses, which could explain why there were more severe effects at lower concentrations.
Saarist led an EPA investigation that found 18 common pharmaceuticals in four rivers and streams in Victoria, including upstream and downstream from wastewater treatment plants. Samples showed common antidepressants, blood pressure, heart and epilepsy medications, caffeine and antibiotics. “What we're dealing with is a cocktail of different drugs,” Saarist said.
The EPA also tested commonly caught fish for drugs. The highest concentrations were of antidepressants, including venlafaxine (150 micrograms per kilogram) in redfin perch and sertraline (100 micrograms per kilogram) in eels. Saarist said there have been no significant human health risks, but regulators are monitoring the situation.
She said people should not flush medicines down the toilet, but instead return unwanted or expired medicines to pharmacies.
“It will be extremely beneficial for the fish that swim in our waterways.”